1. Field of the Invention
This invention relates to cameras in which an operation of the automatic focus adjusting mechanism or the shutter mechanism is initiated by an electromagnet, and more particularly to a malfunction preventing device for such cameras operating in such a manner that no malfunction occurs as accidental actuation of a camera release is prevented.
2. Description of the Prior Art
It has been known in the art to provide a camera in which the shutter mechanism after having been charged in response to a film winding operation and held in the charged position by engaging with a latch member is made to start action when the latch member is taken out of engagement by the attractive force of an electromagnet. Such a device is, for example, disclosed in U.S. Pat. No. 3,722,392 (issued Mar. 27, 1973).
In such cameras, the capacity of the battery which the camera housing can accommodate cannot be very much increased. This applies to the camera of U.S. Pat. No. 3,722,392 too so that it is impossible to achieve a much-desired increase in the intensity of current supplied to the electromagnet and, therefore, to provide a duly large attractive force thereat. As a result, in the case of such camera, it is required that the force necessary to take the latch member out of engagement with the shutter mechanism in the charged position be very small.
However, if so, there will be a high possibility of accidentally releasing the latch member from engagement when the camera receives a shock from the outside (for example, by a force acting thereon when the camera is roughly placed onto a hard surface, or dropped), thus permitting the shutter mechanism to malfunction. Accordingly, such a camera is very susceptible to impulses and encounters a problem from the point of view of practical use.
For this reason, according to the prior art, as disclosed in the above-cited U.S. Pat. No. 3,722,392, means is provided for prohibiting action of the latch member before the actuation of a camera release, and this means is arranged to cooperate with the release actuator in such a manner that the latch member can be moved only after the actuation of camera release, thus preventing a malfunction from occurring before the intentional actuation of the camera release.
However, this conventional method has a disadvantage in that after the release actuator is once operated to initiate an operation of the camera, when the operation of the release actuator is interrupted, it results that despite the camera being under exposure operation, the aforesaid means is actuated again to hinder the action of the latch member so that the exposure operation is stopped from proceeding further. In other words, such a camera is incapable of making a correct exposure when the release actuator is depressed for a moment, and of operation with the use of a self-timer. Also upon consideration of recently developed cameras which generally have automatic focus adjusting devices (hereinafter referred to as "AF"device), even in such cameras, a similar problem arises when the AF device is made to start operating by the attractive force of the electromagnet.